1. Field of the Invention
The present invention relates to an image fluctuation correcting apparatus used for correcting movements, drifts or fluctuation (hereinafter collectively referred to as fluctuations) of pictures or images generated by an image pickup apparatus such as a video camera or the like due to swing, shaking or like movements of the image pickup apparatus which may accompany manipulation thereof.
Recently, in the field of image pickup apparatuses such as video cameras and the like, remarkable progress has been made in implementation of such apparatus having a small size and light weight with a zoom function of high magnification. Besides, the image pickup apparatuses tend to be increasingly used by people of all ages and both sexes. Besides, automatic correcting functions such as auto-focussing function, automatic whitebalance control and automatic luminance control of improved performance have been developed and adopted in many of the commercially available products. On the other hand, there has arisen a problem that image fluctuations occur due to movements of the apparatus, as a result of which the quality of pictures as generated is degraded to great disadvantage. Under the circumstances, there exists a great demand for automatic correction of the image fluctuation.
2. Description of the Prior Art
As a typical method of correcting the image fluctuation, there may be mentioned a method according to which fluctuation of image or picture is detected from picture signals after having taken pictures, wherein positional correction of images or pictures is performed on the basis of the fluctuation information as detected. (Reference may be made to "Technical Reports, Vol. 11, No. 3" published by The Institute of Television Engineers of Japan in May 1987.) More specifically, the picture signal suffering from the image fluctuation undergoes first an analogue-to-digital (A/D) conversion to be subsequently separated into two series, one of which is supplied to a Y/C separation circuit to extract only the Y-signal which is then supplied to a vector detecting circuit. The vector detecting circuit in turn serves for a function to generate an optimum correction vector while being controlled with regard to the area from which the movement vector is to be detected.
As another method of correcting the image fluctuation, it has also been proposed to detect the movements of the image pickup apparatus by means of an angular acceleration sensor to thereby control the position of an imaging unit including an optical system so as to compensate for the movement of the image pickup apparatus. (Reference may be made to "Technical Reports, Vol. 11, No. 2" published by the Institute of Television Engineers of Japan in Nov. 1987.)
Finally, there may be mentioned an image fluctuation correcting method according to which image fluctuation is detected from the picture signal during the image pickup operation for effecting positional correction of the image on the basis of the fluctuation information thus detected, to thereby eliminate the fluctuation. (Reference may be made to IEEE Transactions on Consumer Electronics, Vol. 36, No. 3, August 1990.)
With the methods and systems mentioned above, a field memory or a frame memory is indispensably required when the image fluctuation is to be detected through electronic processing. On the other hand, detection of movements of the image pickup apparatus with the aid of the angular acceleration sensor requires indispensably a position control unit for controlling the imaging unit so as to cancel out or compensate for the movement of the associated image pickup apparatus.